1. Field of the Invention
The present invention relates to program distribution systems, and more specifically, to a program distribution system in which a receiver terminal side discards a received program.
2. Description of the Background Art
In program distribution services that have become available in recent years, not only text data, image data, sound data, etc., but also applications (programs) can be distributed among communications devices over a network. With the distribution of programs, these services can add a new function to receiver terminals, providing functional enhancement thereto. In such program distribution services, JAVA™, is now widely used to achieve a program execution environment independent of any platform. Specifically, a JAVA™ program called an Applet is distributed from a Web server to a Web client over the Internet, and the distributed JAVA™ program is activated on a Web client's terminal. Such JAVA™ program distribution services have also been available for small-sized handheld terminals such as cell phones having a Web browser installed therein.
Furthermore, a system for automatic program distribution has been suggested. In one exemplary system, programs and data are automatically distributed (downloaded) to a mobile terminal that enters a service area.
In such an automatic program distribution system, the distributed programs are always stored in storage areas of a receiver terminal. Consequently, repeated program distribution reduces vacant space of the storage areas, and thus a program that is larger than the vacant space cannot possibly be stored when it is distributed. This is a serious problem especially when the receiver terminal is a cell phone, for example. Therefore, a resource constraint receiver terminal is required.
There is yet another problem in the above automatic program distribution system. In this system, the distributed programs are automatically stored in the receiver terminal without making a user aware of the fact of such storing. Consequently, the user is unaware of the fact that vacant space of the storage areas is being reduced, thereby making the receiver terminal incapable of storing any program that is really desired by the user. To avoid the above-mentioned problems, unwanted programs that are distributed and stored in the receiver terminal should be discarded from the storage areas.
However, it is quite burdensome for the user to delete such unwanted programs manually one by one. To ease such burdens, some techniques are suggested in addition to the above-mentioned manual discarding. For instance, there is a first exemplary technique of presenting use situations of the stored programs to the user. This technique can support the user for deleting unwanted programs. In a second exemplary technique, programs that have not been used over a predetermined period are automatically deleted. In a third exemplary technique, programs are automatically and promptly deleted after they are executed. According to these techniques, programs are automatically deleted, thereby easing a burden of deleting programs from the user.
However, these techniques also have some drawbacks. In the first exemplary technique, a process of deleting the program still has to be manually performed by the user. Therefore, the user's burden cannot be completely eased.
Also, in the second and third exemplary techniques, programs are deleted irrespective of the types or properties of these programs. Consequently, in some cases, deletion may be made against the user's will. For example, it is of course not preferable for some programs, such as paid programs, that are executed at the receiver terminal to be deleted only because they have not been used for the predetermined period, or be promptly deleted after being executed. Therefore, what is suggested in the conventional automatic program deletion techniques is merely applying a certain deletion scheme to all programs without taking the types or properties of these programs in consideration, which leads to possible deletion against the user's will. For this reason, these techniques hardly achieve an appropriate deallocation of the storage areas in the receiver terminal.